Fluid pressure operated engine for well pumps



y 1961 c. L. ENGLISH V R 2,983,227

FLUID PRESSURE OPERATED ENGINE FOR WELL PUMPS Filed June 15, 1959 eet 11 NV EN TOR, 67/ 7/9155 A EA/Gl/SH c. L. ENGLISH 2,983,227 FLUIDPRESSURE OPERATED ENGINE FOR WELL PUMPS May 9, 1961 7 Sheets-Sheet 2Filed June 15, 1959 T 1 r I INVENTOR, 67799455 A. EA/GZ/SH y 1961 c. L.ENGLISH 2,983,227

FLUID PRESSURE OPERATED ENGINE FOR WELL PUMPS Filed June 15, 19592,983,227 FLUID PRESSURE OPERATED ENGINE FOR WELL PUMPS Filed June 15,1959 C. L. ENGLISH May 9, 1961 7 Sheets-Sheet 4 Ta @El/(FQSQL BOTTOM85/5/9594 INVENTOR, 51 6. 7Q. 074 724 s L. 5%2/ 97raeA/EV 2,983,227FLUID PRESSURE OPERATED ENGINE FOR WELL PUMPS Filed June 15, 1959 C. L.ENGLISH May 9, 1961 7 Sheets-Sheet 5 ,Q77'OQA Ef May 9, 1961 c. L.ENGLISH 2,983,227 FLUID PRESSURE OPERATED ENGINE FOR WELL PUMPS FiledJune 15, 1959 '7 Sheets-Sheet 6 DOM/45720.65 CH/ZQCE EVGZ/SH F610. V

[NV EN TOR,

firme/va valve.

FLUID OPERATED ENGINE FOR WELL PUMPS,

Charles L. English, 2204 E. 25th Place, Tulsa, Okla. Filed June is,1959, Ser. No. 820,305 21 Claims. (Cl. 103-46) nected to a combined pumpoperating rod and engine cylinder exhaust conduit, such combinedoperating rod and exhaust conduit extending through a packing gland intoa pump chamber. Under the control of the valve mechanism, operatingfluid pressure will effect reciprocation of the engine piston andconsequently the combined pump operating rod and exhaust conduit, thusefiecting operation of the pump.

One well knownitype of fluid pressure operated reciprocating well pumpincludes elongated engine and pump cylinders arranged end-to-end andspaced apart by a packing gland or middle plug through which extends ahollow so-called middle rod or combined operating rod and exhaustconduit. Within the pump cylinder, the middle rod is connected to asingle acting, valved pump piston, upward movement of which will liftfluid through a production conduit leading to the top of the well, whilewell fluids are drawn into the pump cylinder through a standing valve.Upon downward movement of the pump piston fluid in the pump cylinderbetween the pump piston and the standing valve will pass through thetravelling valve in the piston into the pump cylinder above the Suchreciprocation of the pump piston is effected by appropriate application:of powerfiuid supplied under pressure to the engine cylinder andimposed at all times upon the lower endv of 'the engine piston so as tobias the engine piston upwardly in a power stroke, while the upper endof the engine piston is subjected to exhaust pressure principally, thehydrostatic pressure of fluid in the production tubing leading to thetop of the well, which is less than the operating fluid pressure. Valvemeans are employed to alternately close oflE the communication betweenthe upper end of the engine cylinder and theexhaust conduit ,and toadmit the aforementioned operating fluid pressure'tothe upper enginecylinder. The effectivefluid pressure responsive end area of the upperend of the engine piston is greater than the efiective fluidpressureresponsive area of the lower end of the engine pistontbythecross-sectional area of the middle rod,=so that ,when operating fluidpressure is im-.

posed on both ends, of 'the engine piston a down stroke will occur as aresultpf, a net force in a downward direction. i

Controlof the for reversing 1the porting y enr s ,c a n fififi re ip ocn i 2,983,227 Patented May 9, 1961 "ice ferential end area main valvepiston, and adapted to vary the pressure conditions acting on the mainvalve piston end areas to shift the main valve in opposite directions toreverse the porting. The main valve is co axially disposed in a valvechamber within the engine piston. Actuation of the pilot valve has beeneffected by means of a long thin trip rod extending into the main valvechamber through the upper end of the engine piston, such trip rodextending through an abutment spaced from the engine cylinder, andhaving spaced stops alternately engageable with the abutment to shiftthe pilot valve and thus effect actuation of the main valve as theengine piston approaches the end of its movement in opposite directionsin the engine cylinder.

The aforementioned type of fluid pressure operated pump has proven to beeffective under more or less favorable well conditions, i.e. conditionsof non-gassy well fluids and where the reservoir of well fluids is notpumped off. However, serious failures have resulted in many instanceswhere unfavorable gassy and/or pumped-01f conditions are encountered. Inaddition, the manufacture and assembly of such prior fluid pressureoperated pumps, where long trip rod pilot valve actuation is required,pose various difliculties. Principal among service failures is failureof the trip rods under pumped-off or gassy well conditions, when thepump cylinder contains large quantities of gas "and movement of theengine piston is at such a rate and with such force that tripping of thepilot valve results in undue strain on the trip rod and ultimatefailure.

In accordance with the present invention a fluid pressure operatedengine is provided wherein the engine piston has a main valve chambercoaxially therein, in which the reciprocating main valve is disposed,there being a pilot valve concentrically disposed in the engine pistonand passing entirely through the main valve. In such a construction thepilot valve is so constructed that the pilot valve ports are opened orclosed by reason of the pilot valve being shifted longitudinallyrelative to the engine piston and main valve piston within the confinesof the engine cylinder. Clearly, therefore, a more compact, easilymanufactured engine assembly'is provided, wherein no trip rod need beprovided and the characteristic trip rod failure is obviated while othereconomies are realized.

V A principal object of the invention, then, is'to provide a compact,serviceable fluid pressure operated engine for reciprocating well pumps,wherein the engine comprises an engine cylinder in which isconcentrically disposed an engine piston having a main valve chamberextending coaxially therein, there being a main valve piston shiftablein said chamber to first and second positions for reversing porting insaid engine piston, whereby one end of the engine cylinder isalternately subjected to operating fluid pressure-and exhausted, while apilot valve extends coaxially in the engine piston and through the mainvalve piston, the pilot valve being engageable with abutments in theengine cylinder at opposite ends of ,the engine piston so as tobeshiftedrelative to the engine ment of thelatter and reversal ofthe direction ofmovement of the engine piston. I t

Yet another object is to provide a reciprocating engine structure inaccordance with the principal. objectives hereof, whereina toppilotvalveshift is produced by. elfective engagement .offthe upperextremitygof the pilot valve ,with the top of the engine cylinderSpecifically in-this connection the invention contemplates a top pilotshifter which shiftably extends throughithe top ofthe'engine v pistonand has an external area subjectedto'power fluid pressure duringdownstrokingof the engine piston, wherein the top pilot valve shifter isprovided with a head slidable in an elongated bore for efiecting adash-potting or retardation of movement of the shifter into and out ofthe" engine cylinder, thus to prevent a sudden variation in the volumeof the upper valve chamber at the upper reversal and to minimizedamaging impact of the pilot shifter with the pilot valve stem and withthe piston head.

Still another object is to provide an engine as aforementioned having amain valve and pilot valve construction and porting which are so relatedas to assure complete or eifective pilot controlled main valve reversalprior to reversal of movement of the engine piston to such a substantialextent thatoscillation will result from engine piston reversal takingplace prior to the completion of the pilot valve and main valvereversal.

In the accomplishment of the various aforenoted objectives, as well asothers, the invention contemplates the provision of -a fluid-actuateddeep well pump including, in a combination, a double-acting motor havinga differential end area motor piston interconnected by a hollow rod,with a pump piston reciprocable in a pump cylinder axially aligned withthe motor cylinder. The engine cylinder is ported toenable continuousaccess of operating fluid under pressure to the smaller end of the motorpiston, while as a function of cooperative main and pilot valve meansthe larger end of the motor piston is alternately subjected to powerfluid pressure and to exhaust pressure by reason of the establishment ofintercommunication between the motortcylinder at the larger end of themotor piston and the hollow piston rod interconnecting the motor andpump pistons.

Specifically, the invention contemplates an improvement in thejust-noted pump motor combination, wherein Y the main valve means isfluid-pressure-operated and is disposed concentrically in the motorpiston, the pilot valve means being concentrically disposed in the motorpiston and extending through the main valve so as to control the fluidpressure responsive operation of the main valve to effect shifting ofthe latter, there being abutment means at opposite ends of the motorcylinder for shifting the pilot valve.

. .In such a construction the pilot valve is provided with ports whichalternately establish communication between a valve chamber at one endof the main .valve piston'and a source of fluid under pressure, and apassageway which communicates with the opening through the hollow pistonrod. The pilot'valve ports may be so arranged in the pilot valve stemwith respect to a bore in which the stem is 'slidable that the pilotvalve-ports are --altennately opened and closed so as toalternatelycommunicate with power fluid, which directed to one end of the mainvalve, or to .be subjected to exhaust pressure whereby to relieve saidend of the main valve from power fluid presi sure, so that the mainvalve will be shifted in the other direction through the action of powerfluid acting on said opposite end of the main valve. Moreover, the mainfvalve may shift in the' direction that the engine piston shifts inorder to reverse the engine piston control porting,

or the main .valve may shift ina direction opposite to the direction ofmovement of. the engine piston, as:will more particularly appearhereinafter in the description '-of..the several embodiments of'theinvention hereindisclosed; v

--In the foregoing as well -as in the ensuing description, reference todirection such as top, upstroke, bottom, downstroke and other relatedterminology is withre- "speet tothei ill-ustrative embodiments oftheinvention, and I pre'ssu'ref. as applied to the vvarious pressureresponsive elements for efiecting movement; of the elements is to beunderstood 'as' meaning unlessfothenwise qualified, a"net H H fasuitablepurnber of pisto rm .hydraulie force? workinginan indicateddirection due to ls'imila'r pressure being applied to difierentialareasor due to. ditferential'pressures being applied to like areas.

2,983,227 r I r Ot-her objectives and advantages of the invention willbe hereinafter described or will become apparent to those skilled in theart, and the novel features of the invention will be defined in theappended claims.

Referring to the drawings:

Fig. 1 is a view partly in elevation and pantly in section,'showing afluid-pressure-actuated well pump made in accordance with the invention;

Fig. 2 is a vertical'sectional view through the engine cylinder andengine piston of the fluid-pressure actuated pump of Fig. 1, this viewbeing taken substantially on the compound plane of the line 22 of Fig.3;

Fig. 3 is a transverse sectional view as taken on the line 33 of Fig. 2,and on a slightly enlarged scale;

Fig. 4 is a transverse sectional view as taken on the line 44 of Fig.2,.and on a slightly enlarged scale;

Fig. 5 is a fragmentary vertical sectional view as taken on the line 5-5ofFig. 2;

Fig. 6 is a diagrammatic longitudinal sectional view 0 of thefluidwpressure-actuated pump of Fig. 1, illustrating the condition ofthe main and pilot valve means during downstroking of the engine pistonand on the discharge phase of the pump;

a Fig. 6a is a diagrammatic fragmentary longitudinal 5 sectional viewshowing the engine of Fig. 6 with the pilot and main valves shifted asat the bottom reversal of the engine piston;

Fig. 7 is a diagrammatic longitudinal sectional view of thefluid-pressure-actuatedpump of Fig. 1, illustrating the condition of themain and pilot valve means during upstroking of the engine piston andon-the suction phase of the pump; v

Fig. 7a is 'a diagrammatic fragmentary longitudinal sectional viewshowing the engine of Fig. 6. with the pilot and main valves shifted asat the top reversal of the engine piston, but just prior to theexistence of :a downstroking pressure condition; Y

. Figure 8 is a longitudinal sectional view through a modified form ofengine construction with the main and pilot valve means in condition foreffecting a'downstroke of the engine piston;

Fig. 9 is a view corresponding to Fig. .8 but showing the mainand pilotvalve means in a condition for .eflecting an upstroke of theenginepistom' v, t

Fig. 10. is a longitudinal sectional view through a further nodifiedform of'engine construction with the main and pilot valve means incondition-for effecting a.downstroke of the engine piston; :;v

Fig. 11 is a view corresponding to Fig. 10, but showing 5 themain andpilot valve means in a conditiontor-eifecting an upstroke of the enginepiston.

Fig. 12 is a longitudinal sectionalview through another form of engineconstruction with themain: and pilot valve means in .condition'foreffecting a, downstro'ke. of the engine piston; e

Fig. 13 is a view corresponding to Fig. 12 but showing .the main andpilot valve means in a conditibnfor eifecting an upstroke ofthe-enginepistom' 1 v 7' Referring to Fig. 1, .theexemplaryfluidea'ctuated -pu1np 39 comprises axially aligned-motor an'dpump cylinders 1 and 2 respectively,-threadedly-interconnected at theiradjacent ends by a so-called middleplu'g13-, having therein a packing 4throughwhich extends -ahollow-rniddle rod 5 which as will hereinafterappegiry'constituts a combined piston rod anddischarge-eond'lii-t havinga passage 6extending completelylthereth'rough. I 1 a .Reciprooablydisposed in thef engine' cylinder 'l is a motor-or engine pistongeneralldesignatedM, which is interconnected b'y the middle r'od' 5 with a' pumpplunger or piston generally designated}, The engine .pist'on' M has anenlarged central section 7's lidably"and *sealinglyengaged'with tli i Yi enginecylirider through the mid fluidunderfire'srire is constantlysupplied to the lower portion of the engine cylinder beneath theenlarged central section 7 thereof. Such power fluid is adapted to passinto the engine piston body through a suitable number of ports 10disposed about the engine piston below the enlarged central section 7,and under the control of valve means which will hereinafter beparticularly described, such power fluid is alternately enabled tobypass the enlarged central section 7 of the engine piston and enter theupper portion of the engine cylinder through a suitable number of radialports 11.

Such valve means is also adapted, responsive to the engine pistonsreaching the lower limit of its movement, to exhaust fluid from theupper section of the engine cylinder through the ports -11, and thenceinto the combined piston rod and discharge conduit or middle rod 5,where such exhaust fluid will be co-mingled with fluid being dischargedfrom the pump cylinder 2 during upstroke of the engine piston. Thus themiddle rod 5 is threaded into the pump piston P as at 12, andcommunicates with a bore 13 in the pump piston, which in turncommunicates with a production fluid passage 14 extending through thepump piston P.

The pump piston includes a suitable travelling check valvesuch'as a ballcheck valve 15, while at the lower extremity of the pump cylinder 2there is a bottom plug 16 having therein a ball or other suitable checkor standing valve 17.

Aocordingly,it be noted that an upstroke of the 'en'gine'piston M on aso-called suction stroke will cause the check valve in pump piston P- toclose, so that production fluid in the pump cylinder 2 above the pumppiston P will be discharged, as indicated by the arrows, through asuitable number of production ports 18 extending radially through themiddle plug 3. At the same time, due to the reduction of pressure in thepump cylinder 2' beneath the piston P during the upstroke, well fluidswill unseat the standing valve 17 and pass upwardly therethrough so asto till the pump cylinder 2 beneath the piston P, so that on thesucceeding downstroke of the pump piston P such fluid will transferthrough the travelling valve 15 to the pump cylinder above the piston Pfor ultimate production on the subsequent upstroke of the pump piston P.

In a conventional manner, the assembly shown in Fig. 1 may be loweredinto a pump seat (not shown). As is customary in this connection, thefluid-actuated pump assembly may be of the free pump type, in accordancewith the Dempsey et al. Patent No. 2,653,545, issued September 29, 1953;or as more particularly shown in Dempsey Patent No. 2,63l,54l,'issuedMarch 17, 1953, the fluid-actuated pump assembly of Fig. 1 may beinstalled in a well by securing the pump to a small string of-tubingcommonly called macaroni tubing, and inserting the pump and the macaronitubing string in a larger string of well tubing, which is in turndisposed in the well casing for communication with the well fluids to beproduced. Other known methods of installation may also be availed of.

Referring more particularly to Fig. 2, it will be noted that the enginepiston M comprises a lower body section 19 and an'upper'body section 20threadedly coupled as at 21 beneath the enlarged centralsection 7 of theengine piston. 1

At its upper extremity, the upper body section 20 of the engine piston Mis closed as by means of a plug 22, and at the lower end of the enginepiston M the middle rod 5 is threaded or otherwise suitably secured tothe lower extremity of the piston body section 19 as at 23..

Internally of the upper piston body section 20 is a reduced diametersection 24 which, as best seen in Fig. 3, is provided with a suitableplurality of radially extended portsor openings-ll leading to the enginecylinder space, orchamber above engine piston M, and aplu rality 9 s s.in rrwd with, the

'6 radialports 11 and leading through the reduced diameter section 24.

Seating on the shoulder provided at the upper end of the reduceddiameter section 24 of the piston bodysection 20, is a port collar 27,having ports 28 therethrough which establish communication between thelongitudinally extended ports 26 just referred to, and a lower mainvalve chamber 29 which may be considered to include the space directlybelow the piston head 44.

Abutting with the port collar 27 is a valve cylinder sleeve 39 closelyfitting in the engine piston and in sealing engagement at its upperextremity with the top plug 22 of the engine piston, as indicated at 31.

Abutting with the shoulder provided at the lower end of the reduceddiameter section 24 of the engine piston body 20, is an annular lowervalve seat member 32 which is retained in place by a tubular divider 33,the divider 33 and the seat member 32 being sealed as at 34.

Defined between the divider 33 and the inner periphery of the enlargedcentral section 7 of the engine piston, is an annular passageway 35which communicates with the longitudinally extended ports 26 in thereduced section 24 of the piston body. At its lower extremity thedivider 33 extends into the lower piston body section 19 and is sealedtherewith as at 36.

There is an inwardly directed flange 37 at the lower extremity of thedivider 33 which abuts with an outstanding flange 38 on a tubular pilotvalve guide 39, the flange 38 in turn abutting against a shoulder 40formed in the lower piston body section 19. The lower portion of thepiston body section 19 is provided with a suitable number oflongitudinally extended passages 41 which, as seen in Fig. 4, extendthrough the body along opposite sides of a slot 42 extendingtransversely across the body. The passages 41 communicate at their lowerend with an annular undercut exhaust chamber 43 which is incommunication with the passage 6 through the middle rod 5. At theirupper ends, the passages 41 are in communication with an annular space41a defined between pilot valve means generally indicated at 50 and thedivider 33, such communication being effected through a suitable numberof ports 41b passing through the flange 37 at the base of the divider33. V

Reciprocably disposed within the valve cylinder 30 is a head 44 of amain valve piston generally designated 45, the latter having anelongated stem 46 threadedly or otherwise made integral with the pistonhead 44 and pro jecting through the port collar 27 into the lower valvechamber 29 and into the zone lying between the lower valve seat memberand the port collar 27.

The port collar 27 is provided with an upper valve seat 47, and on thestem 46 between the valve seats 47 and 32 is a plug valve head 48 which,when seated in the lower valve seat 32 as shown in Fig. 2, enablescommunication between the lower valve chamber 29 and the radial ports 11leading to the upper engine cylinder. However, when the plug valve head48 is engaged with the upper valve seat 47 such communication betweenthe lower valve chamber and the radial ports 11 will be cutoff, whilecommunication will be established between such ports 11 and thedischarge passage 6 in the middle rod 5, as will more particularlyappear hereinafter; It is significant to note that the inlet ports '10,the annular passageway 35, longitudinally extended ports 26, port collarports 28 and lower valve chamber 29, con: stitute a transfer passagewaywhereby when the valve head 48 is positioned as shown in Fig. 2,- powerfluid under pressure is transferred from the lower engine cylin: derthrough the engine piston to the upper engine cylinder, so that adownstroke of the enginepiston is effected by reason of the fact thatthe upper end of engine piston M has a larger effectivepressure-responsive area than the lower end of theieng ine piston M, bythe cross-sectional area of themiddle rod 5 whichlextends through themii4 PlQ8 :.1t, a

t-ion 19, and is slidable in said slot.

i: The lower valve chamber 29 being in constant communication with powerfluid under pressure entering the piston M through ports 10, and thelower extremity of the main valve being always subjected to exhaustpressure in the tubular divider 33, it is necessary to apply power fluidunder pressure to the upper valve chamber 49 in orderto provide a nethydraulic force which is effective to shift the valve head 48 intoengagement with the lower valve seat 32 and to maintain such engagement.Alternatively, in order to enable power fluid pressure acting in thelower valve chamber 29 and exhaust pressure acting on the lowerextremity of the valve stem 46 to proyide a net hydraulic force tendingto shift the valve upwardly, it is necessary to establish communicationbetween the upper valve chamber 49 and the exhaust passage 6 through themiddle rod 5. Pilot valve means are provided for alternately admittingpower fluid to the upper valve chamber 49 and exhausting said uppervalve chamber, and in accordance with the invention such pilot valvemeans is concentrically disposed within the engine piston and extendsthrough the main valve previously described.

In the present embodiment, the pilot valve means is generally denoted at50 and includes a tubular pilot valve stem which, in this illustrativeembodiment, is composed of a lower pilot valve section 51 slidablydisposed in a bore 52 extending through the pilot valve guide 39 andextending into the slot 42 in the lower engine piston body section 19Disposed at the upper extremity of the pilot valve section 51 is atubular coupling 53, and operatively connected to this coupling at itsupper extremity is a pilot valve section 53 which extends into a bore 55through the main valve piston and stem.

A passageway 56 is provided through the respective pilot valve sections51, 53 and 54, which is in constant communication with the upper valvechamber 49. The pilot valve section 51 is provided with a lowercross-port 57 and an upper cross-port 58 which are spaced apart adistance less than the length of bore 52. When the pilot valve means 50is in the position shown in Fig. 2, it will be noted that the lowercross-port 57 communicates with a bore 59 in the lower extremity of theguide 37, which constantly contains power fluid under pressure. Suchpowerf fluid enters through the slot 42 in the lower piston body section19. At the same time, it should be noted that the pilot cross-port 58 isclosed, since it is disposed within the confines of the bore 52.Accordingly, power fluid under pressure is free to pass upwardly throughthe Y passageway 56in the pilot valve means and into the reversal of thepilot valve means 50 is preferably accom-l pli'shed by an abutment orsaddle 60 which extends transversely through the slot 42 in the lowerpiston body sec- The saddle 60 is connected at its opposite ends as byscrews 61 to a collar 62 -which is shiftably disposed about the lowerextremity of the piston body section and which is engageable with ashoulder 63 (see Fig. 2) in the middle plug 3. Accordingly, as theengine piston moves downwardly and V as the lower extremity of thelatter moves into a restricted bore 64in the middle plug 3, the collar62 will abut with the'sho'ulder 63, causing the saddle 60 to remainstationary as the piston M continues its downward movement-and a' head65 on the lower extremity' of the pilot valve section 51 abuts with thesaddle 60 so asto hold the pilot valve means stationaryasftheirestof'the assembly continues further downward movement; I Inorder toeffecttop reversal, the pilotvalve means '50 extends upwardlythrough the top plug 22 of the engine piston M for abutting contact withthe upper end 66 of the engine cylinder 1. .In the illustrativeembodiment, the portion of the pilot valve means which extends throughthe top plug 22 is a separate element from the pilot valve section 54and comprises a push rod 67 extending through a bore 68. in the top plug22 for 'engagement with the upper end 66 of the engine cylinder, thepush rod 67 projecting into the upper valve chamber 49 forengagementwith the upper extremity of the pilot valve section 54 as thepush rod 67 is forced into the valve chamber upon abutment of the pushrodwith the top end of the engine cylinder 1.

Preferably as shown in Fig. 2, the top plug 22 is'provided with anenlarged bore 69 in which an enlarged central dash-pot piston 70 isshiftably disposed, said piston 70 being formed on the push rod 67 forthe purpose of dash-potting movement of the push rod. In addition, thelower end of the push rod 67 is provided with a central passage 71 whichcommunicates through a crossport 72 with the bore 69.

Operation of embodiment of F ig. 2

Referring to Fig. 6 wherein the fluidactuated pump is shown in adownstroking. condition similar to that shown in Fig. 2, the structuraldetail of the assembly has been diagrammatically illustrated in order tomore clearly illustrate the path of fluid flow through the various portsand passages in the operation of the engine;

In Fig. 6 the main valve head 48 is engaged with the lowermost valveseat, so that power fluid entering the engine cylinder through ports 9will pass from the lower engine cylinder throngh inlet ports 10, annularpassage way 35, passages 26 and ports 28, into the lower valve chamber,from whence it'will pass through radial ports 11 into the upper enginecylinder, thus providing a net hydraulic force acting on the upper endof the engine piston which will correspondingly effect a downstroke. ofthe pump piston P to close ofl? check valve 17 while check valve 15opens to permit production fluid to pass upwardly therethrough into theupper pump cylinder. At the same time, power fluid passes from thelowerengine cylinder through slot 42 and into the passage 56 in the pilotvalve means through the pilot valve cross-port 57. Accordingly, powerfluid is admitted to the upper valve chamber 49 to provide a nethydraulic forceholding the valve head 48 on the lowermost seat.

For a reason which will hereinafter be more. particularly described, thepush rod 67 is maintained as shown in Fig. 6, projecting to its fullestextent from the upper end of the engine piston.

The annular space 41a defined between the 'divider 33 and the pilotvalve means '50 is, of course, subjected to exhaust pressure throughports 41b and passages 41, lead ing from chamber 43 at the base of thepiston, which chamber is in communication with the exhaust opening 6through the middle rod 5. As will be evident, the

exhaust pressure in the chamber 41a is principally the hydrostatic headof production fluid in a conduit leading to the earths surface. V v VReferring now to Fig.. 6a, the engine piston is shown at the bottom ,ofits downstroke where the bottom reversal of the valve means takes placeDownward movement of the engine piston M has brought collar62 of thepilot valve abutment means into engagement with the stop shoulder 63 asthelower extremity of the engine piston entered the restricted bore 64.Further downward movement has brought the lower extremity of the pilotvalve means 50 into engagement'with' the saddle 60,'thus arrestingfurther downward movement .of the pilot valve means'along with theengine;piston.- Asa result,fthe pilot valve'means has moved within thebore-52 oftthe pilot valve guideand-in the bore 55 through the main'Accordingly, the upper valve chamber 49 has been exhausted through thepilot valve passage 56. In addition, power fluid pressure in the upperengine cylinder will be now acting upon the outer end area of the pushrod 67, while the inner end of the push rod 67 and the annular piston 70are exposed to exhaust pressure, with the result that there will be anet hydraulic force to shift the push rod 67 inwardly. Such inwardmovement of the push rod, however, will be dampened by the dashpoteffect of the piston 70 in the bore 69 to. prevent slamming of the pushrod 67 into the upper extremity of the pilot valve stem. 7

' Due to the exhausting of the upper valve chamber 49,

the effect of power fluid in the lower valve chamber 29- acting upon thedownwardly facing area of the main .valve piston head 44 will provide anet hydraulic force acting upwardly on the main valve to lift the latterand shift the same to the position shown in Fig. 7 where an upstrokecondition exists.

As shown in Fig. 7, the main valve head 48, as a result of theaforementioned net upwardly-acting hydraulic force acting on the mainvalve piston head 44 has been shifted upwardly into engagement with thetop seat 47, so that the fluid pressure transfer passage from inletports 10 to ports llleading to the upper engine cylinder has beenclosedoff, and now the ports 11 are in open communication with the annularchamber 14a which is in constant communication with the exhaust passage6 through the middle rod 5.

It should be noted here that power fluid which is constantly acting onthe lower extremity of the pilot valve means 50, is now efiective toprovide a hydraulic force holding the pilot valve means 50 in the upwardposition as shown in Fig. 7. I

During the upstroke of the fluid-actuated pump production fluid willpass upwardly through the standing check valve 17 into the pump chamberbeneath the pump piston P, while the travelling check valve will beclosed 011 and the enginge exhaust fluid as well as production fluid inthe pump chamber above the pump piston P will be discharged throughports 18 for conduction to the earths surface. I

. .Continued upward movement of the engine piston will bring "the pushrod 67 into engagement with the upper end 66 of the engine cylinder 1 toefieot a shift of the valve means at the top reversal as particularlyillustrated in Fig. 7a. Top reversal-of the valve means is shown in Fig.7a at a stage just prior to the existence of a down-stroking condition,namely, substantially at the midpoint in the pressure-responsive shiftof the main valve.

It will be noted that upward movement of the engine piston has broughtthe push rod 67 into engagement with the upper end of the enginecylinder1, so that the lower extremity of the push rod ,67 contacting the upperend of the pilot valve stem has arrested upward movement of the pilotvalve means while the engine piston and main valve have continued totravel upwardly. Thus, pilot valve cross-port 57 is open tocommunication with power fluid entering through cross-slot 42,. whileupper pilot valve cross-port 5811is' now closed off in the bore 52 ofthe pilot valve guide. 1 q

Accordingly, 'powei-Ifluid now passes through the pilot valve passage 56into. the main'valve chamber 49 to efiect downward movement of the valvepiston, unseating the valve head 48 from the upper valve seat and movingthe valvehead towards-thelower seat. I I

As the valve head reversesthe ports 11, so that they no longercommunicate-with the exhaust chamber 41a but instead progressivelycommunicate with the lower valve chamber 29, power fluid will transferthrough the ports 11 to the upper e'n'gine cylinder to again act uponthe larger end area of the engine piston to drive the same downwardlyv 3,Z'

During the'course of top reversal, downward move ment of :the enginepistonmaycommenceat a time when the pressure in the upper enginecylinder is less than the pressure in the upper valve chamber, since theupper valve chamber 49 must be subjected to power fluid pressure toshift the main valve before the engine piston will reverse. Accordingly,as the engine piston moves away from the upper end of the enginecylinder pressure in the upper valve chamber will force the push rod 67outwardly of the upper valve chamber, but such outward movement of thepush rod is dampened by the dash-pot efiectof the annular piston 70 inthe bore 69 of the upper piston head.

The ratio of the several areas of the main valve are such that undernormal pump operation the degree of pressure in valve chamber 49 capableof moving said main valve to its lower seat is less than the pressurerequired in the upper engine cylinder cavity to institute engine pistonmovement. However, in immediate sequence said cavity 49 will experiencetotal motive pressure as noted due to saturation, whereas the upperengine cylinder cavity will experience less than static mo tive pressuredue to engine piston speed. As a consequence of the mechanical movementof the pilot valve assembly at either end of a stroke, instituting fluidflow to or from the upper valve chamber 49, the several areas of eachthe main valve and pilot valve assembly receive proper motive fluidpressure bias to enforce and/or continue the movement of the pilot valvein the direction instituted and to force both members to their limit oftravel.

Dash-potting of the outward movement of the push rod 67, moreover, isparticularly desirable in those instances where the pump is operating ina gassy well and during the upstroke the lower pump chamber may bepartially filled with gas, under which circumstances, as the enginevalving is reversed the engine piston may commence its downward movementprematurely 'before pressure has effectively transferred from the lowerengine cylinder to the upper engine cylinder.

The just-described cycling of the engine will continue so long as powerfluid is supplied to the engine through the inlet port 9.

From the foregoing description it is apparent that the mode of operationof the fluid-actuated engine is such that the main valve is heldupwardly in the engine piston during upstroke of the latter, and is helddownwardly during down'stroke thereof.

Figures 8 and 9 In Figs. 8 and 9 there is shown an embodiment of theinvention wherein the main valve shifts in a direction oppo'site to thedirection of travel of the engine piston.

Furthermore, in the embodiment first described the pilot valve portingis alternately opened and closed as a result of movement of the pilotvalve cross-ports 57 and 58 alternately into and out of the bore 52 inthe pilot valve guide. In the embodiment of Figs. 8 and 9, however, aswill presently appear, the pilot valve cross-porting is adapted toeffect reversal of the main valve as a result of movement of thecross-porting alternately into and out of a bore in the main valveitself.

In the essential respects the engine cylinder and engine piston of Figs.8 and 9 is similar to that previously described, and accordinglyreference characters in the seriesare employed where applicable.Moreover, the engine cylinder is adapted to be connected in axial alignment to a pump cylinder as in the previously described embodiment. v

Accordingly, referring to Fig. 8 it will be noted thatthe'engine'cylinder 101 is threaded into the middle plug 103 throughwhich extends the middle rod 105 having exhaust passage 106'therethrough. 'Reciprocably disposed in the engine cylinder is themotor piston M which is composed of lower piston body section 119 andupper piston body section .120 threadedly inter-conneeted as at 121.Disposed in the engine piston is a valve cylinder 130 which abuts withthe port collar 127 providing the upper valve seat 147.

Abutting with the reduced diameter central section 124 is a tubulardivider 133 having a lower valve seat 132 formed thereon. The lowervalve chamber 129 is constantly in communication with the exhaustpassage 106 through the middle rod 105, through port' collar ports 128,longitudinally extended passages 126 in the reduced diameter section124, annular space 135 between the divider 133 and the inner wall of thelower piston body section 119, passages 141 through the lower extremityof the piston section 119 and undercut chamber 143 at the lowerextremity of the latter.

Withthe engine in a downstroking condition as shown in Fig. 8, fluidentering through middle plug port 189 will enter through cross-slot 142into the tubular divider 133, land will pass upwardly around the lowerextremity of main valve head 148, through radial ports 111, and thenceinto the upper end of the engine cylinder where a net hydraulic forceurging the engine piston downwardly is provided.

In this embodiment the valve head 148 is removable from the main valvestem 146 and is threaded thereto as at 146a. Moreover, in thisembodiment the pilot valve means 150 comprises an upper push rod 167'shiftably disposed in a bore 168 of top plug 122 of the piston, acentral pilot valve section 154 extending through the bore 155 in themain valve stem, and a lower push rod 167a slidable in the tubulardivider 133.

Pilot valve cross-port 157 communicates with the passageway 1 56extending through the pilot valve section 154. As shown in Fig. 8, thispilot valve cross-port -7 is sealed in the bore of the main valve, sothat power fluid in the passageway 156 of the pilot valve is precludedfrom passing into the upper valve chamber, i.e. upwardly through thevalve piston head 144 of mainvalve piston 145. 7

It will be noted that the valve stem 146 is provided with a chamber 144ain which is reciprocably disposed a pilot valve head 144b, having apassage 144a extending axially. therethrough and communicating with thechamber 144a through angularly disposed ports 144d. Pilot valve porting158 is provided in the piston head 144 in this embodiment by means of anannular chamber 158a in a bore 158b through the valve piston 'head, theporting 158 communicating with the chamber 158a and with the lower valvechamber 129 when the valve means is conditioned for effecting adownstroking of the engine, and the upper valve chamber between pistonhead 144 and top. plug 122 also being opened to exhaust pressure throughan annular clearance 1580 formed in a piston head 170 on upper push rod167 and the bore 158b through the piston head 144.

. With the valve means in the condition shown in Fig. 8, it will benoted that power fluid under pressure acts upon the cross-sectional endarea of the valve head 148 .and

for holding the main valve head 148 in engagement with the upper seat147; i Referring to Fig. 9, the engine is shown at the bottom reversalwith the main valve in a position for enabling the exhaust 'of fluidfromthe'upper engine cylinder. It will be'noted that the lower endof-the pilot valve memher 154 is subjected to power fluid pressure inthe divider 133, and also chamber 144a in the main .valve stem 146 isopen to power fluid pressure passing upwardly through central passageway156 and through pilot valve crossports 157, from which point power fluidpasses upwardly through ports 144d and central passage 144c'in the pilothead 144b into the upper valve chamber between the main valve piston 144and top plug 122.

Under these pressure conditions they piston head 170 on the upper pushrod 167' will be fully seated in dashpot bore .169, so as tojlimitfurther upward movement of the pilot valve means 150 which willbe heldin such position by reason of a net hydraulic force being exerted in anupper direction at the lower extremity of thepilot valve member 154.Thus the pilotvalv'e means is also shifted by hydraulic pressure at thelower reversal, though it is initially unseated mechanically byengagement of the lower push rod 167a with the saddle 160 extendingthrough cross-slot 142 as is shownin Fig. 9.

As in the embodiment previously described, the saddle 160 is suitablysecured to an abutment collar 162 slidable about the lower extremityofthe piston body section 119 and engageable with a'stop shoulder 163 asthe lower extremity of thepiston body section 119 moves into thedash-pot chamber 164. The lower push rod 167a, however, is slidablydisposed within the tubular divider 133 and is centered therein as by asuitable plurality ofradially projecting ribs 167b. At its upperextremity'the push rod 167a is longitudinally ported as at 1670 andtransversely cross-ported at 167d, so as to enable communication ofpower fluid into the passageway 156 through the pilot valve member 154.

A spring 1672 is interposed between a shoulderlfi'l'f internally of thedivider 133 and the ribs 167, so as to normally bias the push rod 167adownwardly, this spring being compressed during mechanical shifting ofthe pilot valve means at the bottom reversal of'the engine as shown inFig. 9.

' 'It should be noted 'in respect to the embodiment of Figs. 8 and 9,that since the main valve head 148 and the engine. piston head move inopposite directions upon reversal of the direction'of travel oftheengine at the end radial ports 111 is minimized. I

V In the embodiment illustrated by Fig.8, the engine piston is biasedfor downstroke movement. The pilot valve assembly in secondary movementwas forced to the position as shown by motivating pressure transferringinto valve member 154 which is exposed to power fluid pressure inthedivider 133. Accordingly, there is provided a nethydraulic force actingon the upper end of push rod 167 which is effective to hold the pilotvalve member 154 in the position shown in Fig. 8, with the head 154thereon engaged at the base of the bore 15%.

, It will be understood that the just-mentioned hydraulic force. becomesavailable at the upper reversal of .the engine .pistonso that the pilotvalve means isefiectively maintained by power fluid pressure in a propercondition the upper engine cylinder cavity reacting against the-area ofbore 168 in greater .force that that of motive pressure acting againstthe area of bore .155; i.e., 168 is greater than 155.

Fig. 9 shows parts positioned for upstroke and it is obvious that thesecondary pilot'valve movementattended a difierential pressuredevelopment between inlet slot 142 andthe' upper engine-cylind'er'cavity before the pilot valve reached the 'position'asillustrated.

It is further obvious that the-area relationship be tween bore 168 andbore will indicate the percentage of pressure variable that must existbetween motive fluid pressure and the pressure existing in the upperengine cylinder cavity to produce, nullify, or reverse theneeded biasfor proper pump function. i p 7 V :Figs'. 10. arid/1'1.

In Figs. 10 and 11 there is shown a furtherntodified constructionwherein, as. inthecase of the. valve means of i fi eanemia lapistbn'kandltlie'.hgine piston travel in opposite directions atthe' topand bottom in the 200 series are employed.

Referring to Fig. 10, the engine piston M is disposed in .the enginecylinder 201, as in the previously described embodiments, includes alower engine piston body section 219 and upper piston body section 220,with a reduced internal central section 224 through which power fluidtransfer ports 211 extend and in which the main valve head 248 isshiftable between upper seat 247 and lower seat 232.

The pilot valve means 250 is adapted to effect reversal of the pressureconditions applicable to the main valve piston 245 so as to alternatelyadmit power fluid to the upper valve chamber between the piston head 244and top plug 222, and to exhaust such power fluid through thelongitudinally extended passageway 25 6 extending through the pilotvalve means 250.

Lower valve chamber 229 is constantly in communication with the exhaustpassage 206 through middle rod 205, via port collar ports 228,longitudinally extended passages 226, annular space 235 between thedivider 233 and the inside wall of the engine piston, and throughlongitudinally extended passageways 241 extending through the lowerpiston body section 219 into exhaust chamber 243.

With the valve means conditioned as shown in Fig. 10, power fluid isfree to enter the tubular divider 233 through cross-slot 242 in whichthe saddle 260 is disposed. Such power fluid is accordingly free to passthrough the fluid pressure transfer passage 211 into the upper enginecylinder to eifect downstroke of the engine piston M.

It should be noted that in this form the pilot valve guide designated239 is elongated and projects as at 239a through a bore 23% in theengine piston body section 219, into the annular discharge chamber 243,Crossports 2390 establish communication between the chamber 243 and anannular chamber 239d within the valve guide 239, and when the engine isdownstroking, as shown in Fig. 10, pilot valve cross-ports 258communicate with the annular chamber 239d, so that the upper valvechamber between main valve piston head 244 and top plug 222 is exhaustedthrough the central passageway 256 through the pilot valve means.

At the same time it should be noted that pilot valve cross-port 257 issealed ofi in bore 252 of the valve guide 239. The lower pilot valvestem 251 containing the cross-ports 257 and 258 extends through anenlarged bore 260a through the saddle 260, and is provided with anoutstanding flange 251a engageable with the saddle 260 to arrestdownward movement of the pilot valve means at the lower end ofthe'downstroke movement of the engine piston.

In this embodiment, the saddle 260 is connected to abutment collar 262by means of a suitable number of diametrically spaced connecting arms262a, the arms 262 being pinned as at 262b to the outer extremities ofthe saddle 260. Assembly of the pin 262b with the saddle 260 andconnecting arms 262a is effected by passage of the 'pin through achordal slot 262c in the lower engine piston body section 219 prior tothe installation of the pilot valve means in the assembly. Followingcomplete assembly of the engine, upward movement of the saddle 260 islimited by the flange 251a so that the pin 262b cannot reach the slot2620.

As shown in Fig. 10, the flange 251:: on the pilot valve member 251 isin engagement with the saddle 260 so that as the lower extremity of thepiston body section 219 moves into the dash-potting bore 264 theabutment collar complete reversal.

,262 will contact shoulder 263; thus limiting further dowe- 252 whilecrossport 257 is opened to power fluid pressure in the bore 260a throughthe saddle 260, as shown in Fig. 11. At this time, power fluid underpressure will passupwardly through the passageway 256 through the pilotvalve means into the upper valve chamber between piston head 244 and topplug 222, so as to eifect reversal of the main valve and consequentengagement of the valve head 248 with the lower seat 232, therebyopening the upper engine cylinder to exhaust through the radial ports211, lower valve chamber 229, port collar ports 228, longitudinallyextended passages 226, annulus 235 and elongated passageways 241, intoannular exhaust chamber 243.

It will be noted that the pilot valve means as shown in Fig. 11 isvirtually hydraulically balanced. However, it is desirable that at theend of the upstroke the pilot valve means be shifted downwardlyhydraulically. This is accomplished by reason of the restriction toexhaust flow through the passage 256 in the pilot valve means from theupper valve chamber, upon closure of pilot valve crossport 257 to powerfluid pressure, and opening ,of'crossport 258 to exhaust pressure inannular space aifording a net hydraulic force acting upon the upperextremity of the upper pilot valve member 254 while saidmain valve ismoving upwardly. If desired, however, the pilot valve means 250 may beso proportioned as to provide a pressure responsive area for shiftingthe pilot valve downwardly independently of movement of the main valve.

At the bottom reversal of course, when the upper engine cylinder isexhausted as aforementioned and the pilot valve crossport 257communicates with power fluid in the bore 260a of saddle 260, powerfluid passes downwardly through pilot valve passageway 256 into thechamber formed at the lower extremity of the valve guide 239 and actsupon the lower extremity of the pilot valve stem 251 to shift the pilotvalve means upwardly.

Accordingly, hydraulic forces are effective at both the top and bottomreversals of the valve means to efiect a I 7 Figs. 12 and 13.

Referring now to Figs. 12 and 13, there is illustrated a furtherembodiment of the. invention incorporating pilot valve porting withinthe pilot valve guide as shown in Figs. 10 and 11 in combination with amain valve construction corresponding generally to that shown in Figs. 8and 9.

The general construction of the assembly of Figs. 12 and 13 is similarto that previously described, and accordingly reference numerals in the300 series are employed, wherein it will be noted that 301 designatesthe motor cylinder in which the motor piston M is reciprocable. Themotor piston again in this form comprises the lower and upper bodysections 319 and 320 respectively.

In the upper piston body section 320 is a valve cylinder 330 in whichthe main valve piston 345 is reciprocable, said main valve piston havinga stem 346 on which is preferably removably secured a ,valve head 348alternately engageable with upper and lower valve seats 347 and 332respectively, during thedownstroke and upstroke, respectively, of theengine piston.

The lower valve chamber 329 communicates through port collar ports 328with longitudinally extended passages 326 leading into annular space 335lying between the tubular divider 333 and the inner wall of the pistonbody, the annulus 335 communicating through longitudinally extendedpassages 341 with annular exhaust space 343 at the base of the enginepiston, and the chamber 343 communicating with passage 306 throughmiddle rod 305.

Reciprocably extending through a bore 368through the top plug 322 of theengine piston, is the push rod 367, having dash-pot piston 370 thereon.The push rod 367 is adapted to engage a shuttle 344b which isreciprocable'in the bore 358b formed in the main valve piston head 344.

Shuttle 344b is provided with a passage 344c there-- through and endpassages 344d for establishing communication between the passage 344sand the chamber formed at the base of the bore 358b, so that when theengine is in the downstroking condition as shown in Fig. 12, fluid isexhausted into the lower valve chamber 329, through angularly disposedpassages 390 communicating with an annulus 391 within the main valvepiston head 344.

Disposed beneath the shuttle 344b and shiftably disposed inthe mainvalve stem 346 is the upper section V 354 of pilot valve means 350. Itshould be understood that the shuttle 344b may if desired be madeintegral with pilot valve section 354. In this embodiment of theinvention the pilot valve portion 354 is integral with the lower pilotvalve section 351, being interconnected by an enlarged central section353. However, the pilot valve passageway 356 is in constantcommunication with power fluid under pressure through crossport 393 atthe juncture of the upper and middle pilot valve sections 354 and 353respectively.

At its upper extremity the pilot valve passageway 356 is blocked 01f asby a plug 394, there being .a crossport .395 through the upper pilotvalve section 354 which is alternately adapted to establishcommunication between the chamber beneath shuttle 344b in bore 358b andto be closed off in the bore 355 through the main valve stem 346. Theengine is in a downstroke condition as shown in Fig. 12, and accordinglythe crossport 395 is closed, while the shuttle is in a position openingthe upper valve chamber between the main valvepiston 344 andthe top plug322 to exhaust as aforementioned.

member 351 communicating with the chamber 339d through crossports 396,so that the chamber 397 at the bottom of the bore 352 in the valveguide339 is open to exhaust pressure.

' As the engine piston approaches the-lower limit of its porting willbereversed, as shown .in Fig. 13.

.- As shown in this latter view, there is a crossport 398 extendingthrough the lower section 351 of the pilot valve meanswhichlconnnunicates with the central passageway 395 therein, so thatpower fluid under pressure is'admitted into the chamber 397 at the baseof the bore 352 in guide .339. In addition,. crossport 395 at the upperend of the upper pilot valve section 354.. is caused to commuhicate withthe chamber beneath the shuttle 34411,

so that power fluid under pressure passes through crossslot 342 in theengine piston upwardly through divider 333 so as to act upon the lowerend of the main valve stem 346, while power fluid passes upwardlythrough pilot valve passage 356 and through crossport 395, and thenceupwardly through passage 344a in the shuttle 344b, into the uppervalvechamber between thegmain valve piston head 344 and the top plug322.

Accordingly, the main valve head 348 will be held on the lower seat 332while the pilot valve means is maintained in an upward position as shownin Fig. 13 due to the net hydraulic force applied to the lower extremityof the pilot valve means in the chamber 397, it being noted that thepilot valve means is hydraulically balanced except for the end thereofin chamber 397 and the upper extremity of the push rod 367 which, in theupstroke condition, is exposed to exhaust pressure in the upper enginechamber.

Thus during both the upstroke and. downstroke of the engine piston,pilot valve action is mechanically initiated followed by hydraulicoperation by selectively proportioning the cross-sectional areas of thepilot valve components.

While the various details of the several embodiments of the inventionhave been herein shown and described, changes and alterations may beresortedt'o without departing from the spirit of the invention asdefined in the appended claims. Particularly, cross-sectionalrelationships may be varied so as to efiect the desired variations inhydraulic response of the engine piston, main valve piston and pilotvalve means, as may be required for opera'tion of the pump in wellswherein different operating conditions obtain.

In each of the several embodiments herein disclosed,

the primary movement of the pilot valve assembly is mecham'cally shiftedinto reversing position by the nethydraulic bias of the engine piston asit approaches its limit of travel at either end of a total stroke. Themanner in which this primary movement of the pilot valve is instrumentedrepresents one. phase of valve improvement. For many inherent reasons itis obvious that additional latitude for pilot valve movement beyond thelimit of hydraulic bias of the engine piston must be provided the pilotvalve. This over-ride or secondary movement of the pilot valve isenforced by a net hydraulic'force reacting coincidentally and/orseparately upon both the main valve and pilot valve as hereinbeforestated.

During normal pump operation, the engine piston is enforcedin downstrokemovement by a near total motive fluid pressure in the upper enginecylinder cavity and in upstroke movement by a near'exhaust fluidpressure in said engine cylinder cavity. Under conditions of totalcavitation in the lower pump (suction) chamber (critically abnormalpumping conditions) the engine piston cycle will be enforced with theabove pressure conditions substantially reversed in said upper enginecavity. This 'condition rapidly diminishes as enginepiston moves upwardfrom its position of lower limit turn-about. In like manner down-strokemovement of the enginepiston when 'under total and/or partialpumpchamber cavitation (near normal pumping condition) will be enforced byempounded exhaust fluid pressure, reacting against the top face of thepump piston plus a total reversal of nor, mal pressure requirement in'the upper engine cylinder cavity. As .engine piston moves away from.its: upper limit turn-about power demand created bycompression in lowerpump piston cavity inducesrequirement in the upper engine piston chamberto increase-towards normal pressure value. I

A near-normal pumping condition exists when the pump piston in downwardmovement encounters anddisplaces liquid by the time that pilotvalve-means have been mechanically shifted to reversing position. ltisevident that the ensuing secondary movement of said, valve will beenforced under normal upper engine cylinder pressure conditions. Thisnear-normal pumping condition must be considered as standard for amajority of pump installations because the operator will consistentlyoperate' his equipment beyond well capacity. For this reason the valvemeans herein referred to, with the exceptions of Fig. 8 and Fig. 9 (aspreviously noted) are" designed with ample latitude given the topturn-about.

The main valve and parts 51 and 54 of the pilot valve are soproportioned that the thrust of motive fluid pressure plus the thrust ofexhaust fluid pressure reacting in one direction are balanced by anincreasing or decreasing pressure in the upper valve cavity 49. It hasbeen found that when the apparent balancing pressure of cavity 49assumes a pressure equal to the exhaust fluid pressure plusapproximately one-half the differential between the motive and exhaustfluid pressures, both members of the valve means proceed in nearsimultaneous accord to a completely reversed position. This action iseasily ap parent with reference top reversal as indicated in Fig. 7a.

Under conditions of complete pump chamber cavitation, the piston unit isinhibited from instantaneous reverse movement (re. Fig. 6a) by thekenetic energy developed in retrograde fluid flow down the productiontubing plus the inertia of instituting the flow of said liquid movementup said tubing. This momentary hesitation allows complete liquid exhaustfrom upper valve chamber 49 as said exhaust relates to valve meansmovement. The downward bias of the pilot valve assembly (i.e., 51 and54, plus 67) is held by abutment member 60 during the interval thatmotive fluid pressure commands the top face of 67 (upper valve chamber)plus the exhausting pressure of 49 induced by the upward thrust of mainvalve until said main valve comes to rest against its seat. Theproportionate values of parts 51, 54 and 67 are such that its constantupward fluid pressure bias overcomes the downward bias of the totalmotive pressure intensity residing in the upper engine cylinder cavityplus a safe degree of residue pressure exhausting from cavity 49 at theinstant the main valve reaches at rest position before the piston unitreceives suflicient bias to move.

I claim:

1. In a fluid-actuated deep well pump comprising the combination of adouble-acting motor including a cylinder and a motor piston reciprocabletherein, said piston having oppositely directed faces of differentareas, the smaller of said faces being adapted to be in continuous opencommunication with a source of operating fluid; a pump including acylinder and a pump piston reciprocable therein, a piston rodinterconnecting said pump and motor pistons, said rod having a fluidpassageway extending axially therethrough and communicating at one endwith said pump cylinder; and valve means carried by said motor pistonand operable to provide communication between the larger of said motorpiston faces and alternately, said source of operating fluid and saidfluid passageway in said piston rod; the improvement wherein said valvemeans includes fluid pressure operated main valve means concentricallydisposed in said motor piston, pilot valve means concentrically disposedin said main valve means and reciprocable therein for controlling thefluid pressure responsive operation of said main valve means to shiftsaid main valve means, and abutment means within said motor cylinder atopposite ends of said motor cylinder for shifting said pilot valvemeans.

2. A fluid-actuated deepwell pump as defined in claim 1, wherein saidabutment means includes a member shiftably carried by said motor pistonand engageable with the end of said motor cylinder.

3. A fluid-actuated deep well pump as defined in claim 1, wherein saidabutment means at one end of the motor piston includes a push rodreciprocably extending through said end of the motor piston forengagement with the adjacent end of the motor cylinder.

4. A fluid-actuated deep well pump as defined in claim 18 3, includingmeans for dashpotting reciprocation of said push rod.

5. A fluid-actuated deep well pump as defined in claim 1, wherein saidabutment means at one end of the motor piston includes a saddleextending transversely through said motor piston, and a member slidablymounted on said motor piston and connected to said saddle, said motorcylinder end adjacent to said slidable member having a shoulderengageable by said slidable member.

6. In a fluid-actuated deep well pump comprising the combination of adouble-acting motor including a cylinder and motor piston reciprocabletherein, said piston having oppositely directed faces of differentareas, the smaller of said faces being adapted to be in continuous opencommunication with a source of operating fluid; a pump including acylinder and a pump piston reciprocable therein; a piston rodinterconnecting said pump and motor pistons, said rod having a fluidpassageway extending axially therethrough and communicating at one endwith said pump cylinder; and valve means carried. by said motor pistonand'operable to provide communication between the larger of said motorpiston faces and alternately, said source of operating fluid and saidfluid passageway in said piston rod; the improvement wherein said valvemeans includes fluid pressure operated main valve means concentricallydisposed in said motor piston, pilot valve means concentrically disposedin said main valve means and reciprocable therein for controlling thefluid pressure responsive operation of said main valve means to shiftsaid main valve means, abutment means at op posite ends of said motorcylinder for shifting said pilot valve means, and means for dashpottingmovement of said pilot valve means.

7. In a fluid-actuated deep well pump comprising the combination of adouble-acting motor including a cylinder and a motor piston reciprocabletherein, said piston having oppositely directed faces of differentareas, the smaller of said faces being adapted to be in continuous opencommunication with a source of operating fluid; a pump including acylinder and a pump piston reciprocable therein; a piston rodinterconnecting said pump and motor pistons, said rod having a fluidpassageway extending axially therethrough and communicating at one endwith said pump cylinder; and valve means carried by said motor pistonand operable to provide communication between the larger of said motorpiston faces and al- .ternately, said source of operating fluid and saidfluid passageway in said piston rod; the improvement wherein said valvemeans includes fluid pressure operated main valve means concentricallydisposed in said motor piston, pilot valve means concentrically disposedin said main valve means and reciprocable therein for controlling thefluid pressure responsive operation of said main valve means to shiftsaid main valve means and extending through said motor piston at one endfor engagement with the end of said motor cylinder to effect movement ofsaid pilot valve means in one direction, and abutment means engageablewith said pilot valve means at the other end of said motor piston forshifting said pilot valve means in the other direction.

8. In a fluid-actuated deep well pump comprising the combination of adouble-acting motor including a cylinder and a motor piston reciprocabletherein, said piston having oppositely directed faces of differnt area,the smaller of said faces being adapted to be in continuous opencommunication with a source of operating fluid; a pump including acylinder and a pump piston reciprocable therein; a piston rodinterconnecting said pump and motor pistons, said rod having a fluidexhaust passageway extending axially therethrough and communicating atone end with said pump cylinder; and valve means carried by said motorpiston and operable to pro vide communication between the larger of saidmotor piston faces and alternately, said source of operating fluid andsaid fluid passageway in said piston rod; the improvement wherein saidvalve means includes fluidpressure operated main valve means.concentrically disposed in saidmotor piston, pilot valve meansconcentrically disposed in said main valve means and reciprocabletherein for controlling the fluid pressure responsive operation of saidmain valve means to shift said main valve means, abutment means atopposite ends of said motor cylinder forshifting said pilot valve means,said main valve means including a valve piston having differential 'endareas, and said pilot valve means having ports alternately establishingcommunication between the larger of said main valve piston end areas andsaid source of fluid under pressure and said passageway in said pistonrod upon movement of said pilot valve means in opposite directions.

9. A fluid-actuated deep well pump as defined in claim 8, wherein saidpilot valve 'means is provided with a passage therethrough in constantcommunication. with the larger end area of said main valve piston andwith said ports.

10. A fluid-actuated deep well pump as defined in claim 8, wherein saidpilot valve means includes a stem having a passage extendinglongitudinally thereof and communicating with said ports, said motorpiston having a bore in which said stem is slidably disposed with saidstem exposed to said power fluid at one end of the bore and to thepressure of fluid in said exhaust passageway at the other end of saidbore, said ports being located in relation along said stem so that saidports are exposed at one end of the bore upon movement of said stem inone direction and at the other end of said bore upon movement of saidstern in the other direction.

11. A fluid-actuated deep well pump as defined in claim 8, wherein saidpilot valve means includes a stem having a passage extendinglongitudinally thereof and communicating with said ports, said motorpiston having a bore closed at one end in which one end of said stem isslidably disposed, said bore being in communication with said exhaustpassageway, and said ports being spaced along said stem so as toalternately establish communication through said ports between saidexhaust passageway and said passage in said stem and between saidpassage in said stern and said source of operating fluid upon movementof said stem in opposite directions.

12. In a fluid-pressure operated motor pump comprising an enginecylinder and a pump cylinder below said engine cylinder, an enginepiston reciprocable in said engine cylinder, a pump piston reciprocablein said pump cylinder, a hollow rod connecting said engine and pumppistons, said engine cylinder having a power fluid inlet portcommunicating with the lower end of the engine cylinder, passageways forconducting fluid from the lower end of the engine cylinder to the upperend thereof and for exhausting fluid from the upper end of the enginecylinder into said hollow rod, and valve means for alternatelypermitting and preventing the flow of fluid into and the exhaust offluid from the upper end of said engine cylinder, that improvementwherein saidvalve means includes a fluid pressure operated main valveconcentrically disposed in said engine piston, pilot valve meansextending coaxially through said main valve for reversing the effect offluid pressure on said main valve upon reciprocation of said pilot valvemeans, and means wholly within said engine cylinder for shifting saidpilot valve in opposite directions when said engine piston approachesthe end of its movement in opposite directions in said engine cylinder.

13. A fluid operated reciprocating engine comprising a cylinder, anengine piston reciprocable in said'cylinder, valve means to control theapplication of diflerential mo tive fluid pressures to said cylinder atopposite ends of the engine piston, said valve means including a mainvalve piston, said engine piston having a valve chamber extendingaxially therein in which said main valve piston is disposed, pilot valvemeans extending coaxially through said main valve'piston for controllingthe application of said main valve piston, and means wholly within saidcylinder for effecting reciprocation of said pilot valve means as saidengine piston. approaches the end of its movement in said cylinder inopposite directions.

14. A fluid operated reciprocating engine as defined in claim 13,wherein said pilot valve means projects through one end of said enginepiston for abutting engagement with the adjacent end of said cylinderupon movement of said engine piston in one direction, and includingrelatively stationary means engageable with said pilot valve means uponmovement of the engine piston in the opposite direction.

l5. Afluid operated reciprocating engine as defined in claim 13, whereinsaid pilot valve means includes fluid pressure responsive areassubjected to fluid pressure for biasing said pilot valve means inopposite directions.

16. A fluid operated reciprocating engine as defined in claim 13,wherein said pilot valve means includes fluid pressure responsive areassubjected to fluid pressure for biasing said pilot valve means in onedirection.

'17. In a fluid operated reciprocating engine comprising a cylinder, anengine piston reciprocable in said cylinder and having differential endareas whereby operating fluid under pressure admitted to said cylinderat opposite ends of said piston and alternately exhausted from saidcylinder at the larger end of said piston will eflect reciprocation ofthe piston, the improvement comprising valve means to control the flowof power fluid to and exhaust from said cylinder at the larger end ofthe piston, said valve means including a dilierential end area mainvalve piston, said. engine piston having a valve chamber extendingaxially therein in which said main valve piston is disposed, pilot valvemeans extending coaxially through said main valve piston for alternatelyadmitting power fluid to said valve chamber at the larger end of saidmain valve piston and exhausting said valve chamber upon reciprocationof said pilot valve means, and means wholly within said cylinder foreflecting reciprocation of said pilot valve means as said engine pistonapproaches theend of its movement in said cylinder in oppositedirections.

18. A fluid operated reciprocating engine as defined in claim 17,wherein said pilot valve means includes a stem having a longitudinallyextended passage therethrough and axially spaced transverse portscommunicating with said passage, said engine and main valve pistonshaving bores in which said stem is shiftably disposed, said transverseports being spaced along said stem so that said passage in said stemalternately communicates through said passages with operating fluid andwith exhaust and said ports are alternately sealed off in one of saidbores upon reciprocation of said stem, and said passage in said stemcommunicating with said main valve chamber at one side of the main valvepiston upon movement of the pilot valve means in one direction.

19. A fluid pressure operated engine for reciprocating Well pumps,comprising an engine cylinder, a diflerential end area piston shiftablydisposed in said cylinder, said cylinder having an inlet port for theadmission of power fluid, said piston having a valve chamber therein, apressure transfer passageway for establishing communication between saidvalve chamber and said cylinder, and an exhaust passage communicatingwith said valve chamber and leading from said engine cylinder, valvemeans for alternately interrupting and permitting flow of fluid throughsaid pressure transfer passageway and through said valve chamber fromsaid cylinder to said exhaust passage, said valve means including avalve piston shiftably disposed in said valve chamber, and pilot valvemeans extending coaxially with respect to said valve piston and saidengine piston, said pilot valve means having a passageway foralternately admitting fluid to and exhausting fluid from said valvechamber at one end of said valve piston upon reciprocation of said pilotvalve means,

speaks? 21 and abutment means at opposite ends of said engine cylinderfor engaging and shifting said pilot valve means as said engine pistonapproaches the opposite ends of said cylinder.

20. A fluid pressure operated engine for reciprocating well pumps,comprising an engine cylinder, a differential end area piston shiftablydisposed in said cylinder, said cylinder having an inlet port for theadmission of power fluid into the cylinder between the smaller end ofsaid piston and one end of the cylinder, said piston having a valvechamber therein, a pressure transfer passageway for establishingcommunication between said valve chamber and said cylinder at oppositeends of said piston, and an exhaust passage communicating with saidvalve chamber and leading from said engine cylinder, valve means foralternately interrupting and permitting flow of fluid through saidpressure transfer passageway and through said valve chamber from saidcylinder at the larger end of said piston to said exhaust passage, saidvalve means including a valve piston shiftably disposed in said valvechamber, and pilot valve means extending coaxially with respect to saidvalve piston and said engine piston, said pilot valve means having apassageway for alternately admitting fluid to and exhausting fluid fromsaid valve chamber at one end of said valve piston upon reciproca- :tionof said pilot valve means, and abutment means at opposite ends of saidengine cylinder for engaging and shifting said pilot valve means as saidengine piston approaches the opposite ends of said cylinder.

21. A fluid pressure operated engine for reciprocating well pumps,comprising an engine cylinder, a difierential end area piston shiftablydisposed in said cylinder, said cylinder having an inlet port for theadmission of power fluid into the cylinder between the smaller end ofsaid piston and one end of the cylinder, said piston having a valvechamber therein, a premure transfer passageway for establishingcommunicating between said valve chamber and said cylinder at oppositeends of said piston, and an exhaust passage communicating with saidvalve chamber and leading from said engine cylinder, valve means foralternately interrupting and permitting flow of fluid through saidpressure transfer passageway and through said valve chamber from saidcylinder at the larger end of said piston to'said exhaust passage, saidvalve means including a valve piston shiftably disposed in said valvechamber, said valve piston having a head thereon provided with axiallyspaced opposed seating surfaces, axially spaced seats for said valvehead, said pressure transfer passageway passing between said seats, andpilot valve means extending coaxially with respect to said valve pistonand said engine piston, said pilot valve means having a passageway foralternately admitting fluid to and exhausting fluid from said valvechamber at one end of said valve piston upon reciprocation of said pilotvalve means to efiect alternate engagement of said seating surfaces onsaid valve head with said seats, and abutment means at opposite ends ofsaid engine cylinder for engaging and shifting said pilot valve means assaid engine piston approaches the opposite ends of said cylinder.

References Cited in the file of this patent UNITED STATES PATENTS437,806 Weatherhead Oct. 7, 1890 585,083 Cook June 22, 1897 825,950 WeirJuly 17, 1906 2,134,174 Coberly Oct. 25, 1938 2,631,541 Dempsey Mar. 17,1953 2,631,572 Dempsey Mar. 17, 1953 2,751,889 Mohler June 26, 1956

